1 /* 2 * CMAC: Cipher Block Mode for Authentication 3 * 4 * Copyright © 2013 Jussi Kivilinna <jussi.kivilinna@iki.fi> 5 * 6 * Based on work by: 7 * Copyright © 2013 Tom St Denis <tstdenis@elliptictech.com> 8 * Based on crypto/xcbc.c: 9 * Copyright © 2006 USAGI/WIDE Project, 10 * Author: Kazunori Miyazawa <miyazawa@linux-ipv6.org> 11 * 12 * This program is free software; you can redistribute it and/or modify 13 * it under the terms of the GNU General Public License as published by 14 * the Free Software Foundation; either version 2 of the License, or 15 * (at your option) any later version. 16 * 17 */ 18 19 #include <crypto/internal/hash.h> 20 #include <linux/err.h> 21 #include <linux/kernel.h> 22 #include <linux/module.h> 23 24 /* 25 * +------------------------ 26 * | <parent tfm> 27 * +------------------------ 28 * | cmac_tfm_ctx 29 * +------------------------ 30 * | consts (block size * 2) 31 * +------------------------ 32 */ 33 struct cmac_tfm_ctx { 34 struct crypto_cipher *child; 35 u8 ctx[]; 36 }; 37 38 /* 39 * +------------------------ 40 * | <shash desc> 41 * +------------------------ 42 * | cmac_desc_ctx 43 * +------------------------ 44 * | odds (block size) 45 * +------------------------ 46 * | prev (block size) 47 * +------------------------ 48 */ 49 struct cmac_desc_ctx { 50 unsigned int len; 51 u8 ctx[]; 52 }; 53 54 static int crypto_cmac_digest_setkey(struct crypto_shash *parent, 55 const u8 *inkey, unsigned int keylen) 56 { 57 unsigned long alignmask = crypto_shash_alignmask(parent); 58 struct cmac_tfm_ctx *ctx = crypto_shash_ctx(parent); 59 unsigned int bs = crypto_shash_blocksize(parent); 60 __be64 *consts = PTR_ALIGN((void *)ctx->ctx, 61 (alignmask | (__alignof__(__be64) - 1)) + 1); 62 u64 _const[2]; 63 int i, err = 0; 64 u8 msb_mask, gfmask; 65 66 err = crypto_cipher_setkey(ctx->child, inkey, keylen); 67 if (err) 68 return err; 69 70 /* encrypt the zero block */ 71 memset(consts, 0, bs); 72 crypto_cipher_encrypt_one(ctx->child, (u8 *)consts, (u8 *)consts); 73 74 switch (bs) { 75 case 16: 76 gfmask = 0x87; 77 _const[0] = be64_to_cpu(consts[1]); 78 _const[1] = be64_to_cpu(consts[0]); 79 80 /* gf(2^128) multiply zero-ciphertext with u and u^2 */ 81 for (i = 0; i < 4; i += 2) { 82 msb_mask = ((s64)_const[1] >> 63) & gfmask; 83 _const[1] = (_const[1] << 1) | (_const[0] >> 63); 84 _const[0] = (_const[0] << 1) ^ msb_mask; 85 86 consts[i + 0] = cpu_to_be64(_const[1]); 87 consts[i + 1] = cpu_to_be64(_const[0]); 88 } 89 90 break; 91 case 8: 92 gfmask = 0x1B; 93 _const[0] = be64_to_cpu(consts[0]); 94 95 /* gf(2^64) multiply zero-ciphertext with u and u^2 */ 96 for (i = 0; i < 2; i++) { 97 msb_mask = ((s64)_const[0] >> 63) & gfmask; 98 _const[0] = (_const[0] << 1) ^ msb_mask; 99 100 consts[i] = cpu_to_be64(_const[0]); 101 } 102 103 break; 104 } 105 106 return 0; 107 } 108 109 static int crypto_cmac_digest_init(struct shash_desc *pdesc) 110 { 111 unsigned long alignmask = crypto_shash_alignmask(pdesc->tfm); 112 struct cmac_desc_ctx *ctx = shash_desc_ctx(pdesc); 113 int bs = crypto_shash_blocksize(pdesc->tfm); 114 u8 *prev = PTR_ALIGN((void *)ctx->ctx, alignmask + 1) + bs; 115 116 ctx->len = 0; 117 memset(prev, 0, bs); 118 119 return 0; 120 } 121 122 static int crypto_cmac_digest_update(struct shash_desc *pdesc, const u8 *p, 123 unsigned int len) 124 { 125 struct crypto_shash *parent = pdesc->tfm; 126 unsigned long alignmask = crypto_shash_alignmask(parent); 127 struct cmac_tfm_ctx *tctx = crypto_shash_ctx(parent); 128 struct cmac_desc_ctx *ctx = shash_desc_ctx(pdesc); 129 struct crypto_cipher *tfm = tctx->child; 130 int bs = crypto_shash_blocksize(parent); 131 u8 *odds = PTR_ALIGN((void *)ctx->ctx, alignmask + 1); 132 u8 *prev = odds + bs; 133 134 /* checking the data can fill the block */ 135 if ((ctx->len + len) <= bs) { 136 memcpy(odds + ctx->len, p, len); 137 ctx->len += len; 138 return 0; 139 } 140 141 /* filling odds with new data and encrypting it */ 142 memcpy(odds + ctx->len, p, bs - ctx->len); 143 len -= bs - ctx->len; 144 p += bs - ctx->len; 145 146 crypto_xor(prev, odds, bs); 147 crypto_cipher_encrypt_one(tfm, prev, prev); 148 149 /* clearing the length */ 150 ctx->len = 0; 151 152 /* encrypting the rest of data */ 153 while (len > bs) { 154 crypto_xor(prev, p, bs); 155 crypto_cipher_encrypt_one(tfm, prev, prev); 156 p += bs; 157 len -= bs; 158 } 159 160 /* keeping the surplus of blocksize */ 161 if (len) { 162 memcpy(odds, p, len); 163 ctx->len = len; 164 } 165 166 return 0; 167 } 168 169 static int crypto_cmac_digest_final(struct shash_desc *pdesc, u8 *out) 170 { 171 struct crypto_shash *parent = pdesc->tfm; 172 unsigned long alignmask = crypto_shash_alignmask(parent); 173 struct cmac_tfm_ctx *tctx = crypto_shash_ctx(parent); 174 struct cmac_desc_ctx *ctx = shash_desc_ctx(pdesc); 175 struct crypto_cipher *tfm = tctx->child; 176 int bs = crypto_shash_blocksize(parent); 177 u8 *consts = PTR_ALIGN((void *)tctx->ctx, 178 (alignmask | (__alignof__(__be64) - 1)) + 1); 179 u8 *odds = PTR_ALIGN((void *)ctx->ctx, alignmask + 1); 180 u8 *prev = odds + bs; 181 unsigned int offset = 0; 182 183 if (ctx->len != bs) { 184 unsigned int rlen; 185 u8 *p = odds + ctx->len; 186 187 *p = 0x80; 188 p++; 189 190 rlen = bs - ctx->len - 1; 191 if (rlen) 192 memset(p, 0, rlen); 193 194 offset += bs; 195 } 196 197 crypto_xor(prev, odds, bs); 198 crypto_xor(prev, consts + offset, bs); 199 200 crypto_cipher_encrypt_one(tfm, out, prev); 201 202 return 0; 203 } 204 205 static int cmac_init_tfm(struct crypto_tfm *tfm) 206 { 207 struct crypto_cipher *cipher; 208 struct crypto_instance *inst = (void *)tfm->__crt_alg; 209 struct crypto_spawn *spawn = crypto_instance_ctx(inst); 210 struct cmac_tfm_ctx *ctx = crypto_tfm_ctx(tfm); 211 212 cipher = crypto_spawn_cipher(spawn); 213 if (IS_ERR(cipher)) 214 return PTR_ERR(cipher); 215 216 ctx->child = cipher; 217 218 return 0; 219 }; 220 221 static void cmac_exit_tfm(struct crypto_tfm *tfm) 222 { 223 struct cmac_tfm_ctx *ctx = crypto_tfm_ctx(tfm); 224 crypto_free_cipher(ctx->child); 225 } 226 227 static int cmac_create(struct crypto_template *tmpl, struct rtattr **tb) 228 { 229 struct shash_instance *inst; 230 struct crypto_alg *alg; 231 unsigned long alignmask; 232 int err; 233 234 err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SHASH); 235 if (err) 236 return err; 237 238 alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_CIPHER, 239 CRYPTO_ALG_TYPE_MASK); 240 if (IS_ERR(alg)) 241 return PTR_ERR(alg); 242 243 switch (alg->cra_blocksize) { 244 case 16: 245 case 8: 246 break; 247 default: 248 err = -EINVAL; 249 goto out_put_alg; 250 } 251 252 inst = shash_alloc_instance("cmac", alg); 253 err = PTR_ERR(inst); 254 if (IS_ERR(inst)) 255 goto out_put_alg; 256 257 err = crypto_init_spawn(shash_instance_ctx(inst), alg, 258 shash_crypto_instance(inst), 259 CRYPTO_ALG_TYPE_MASK); 260 if (err) 261 goto out_free_inst; 262 263 alignmask = alg->cra_alignmask; 264 inst->alg.base.cra_alignmask = alignmask; 265 inst->alg.base.cra_priority = alg->cra_priority; 266 inst->alg.base.cra_blocksize = alg->cra_blocksize; 267 268 inst->alg.digestsize = alg->cra_blocksize; 269 inst->alg.descsize = 270 ALIGN(sizeof(struct cmac_desc_ctx), crypto_tfm_ctx_alignment()) 271 + (alignmask & ~(crypto_tfm_ctx_alignment() - 1)) 272 + alg->cra_blocksize * 2; 273 274 inst->alg.base.cra_ctxsize = 275 ALIGN(sizeof(struct cmac_tfm_ctx), crypto_tfm_ctx_alignment()) 276 + ((alignmask | (__alignof__(__be64) - 1)) & 277 ~(crypto_tfm_ctx_alignment() - 1)) 278 + alg->cra_blocksize * 2; 279 280 inst->alg.base.cra_init = cmac_init_tfm; 281 inst->alg.base.cra_exit = cmac_exit_tfm; 282 283 inst->alg.init = crypto_cmac_digest_init; 284 inst->alg.update = crypto_cmac_digest_update; 285 inst->alg.final = crypto_cmac_digest_final; 286 inst->alg.setkey = crypto_cmac_digest_setkey; 287 288 err = shash_register_instance(tmpl, inst); 289 if (err) { 290 out_free_inst: 291 shash_free_instance(shash_crypto_instance(inst)); 292 } 293 294 out_put_alg: 295 crypto_mod_put(alg); 296 return err; 297 } 298 299 static struct crypto_template crypto_cmac_tmpl = { 300 .name = "cmac", 301 .create = cmac_create, 302 .free = shash_free_instance, 303 .module = THIS_MODULE, 304 }; 305 306 static int __init crypto_cmac_module_init(void) 307 { 308 return crypto_register_template(&crypto_cmac_tmpl); 309 } 310 311 static void __exit crypto_cmac_module_exit(void) 312 { 313 crypto_unregister_template(&crypto_cmac_tmpl); 314 } 315 316 module_init(crypto_cmac_module_init); 317 module_exit(crypto_cmac_module_exit); 318 319 MODULE_LICENSE("GPL"); 320 MODULE_DESCRIPTION("CMAC keyed hash algorithm"); 321 MODULE_ALIAS_CRYPTO("cmac"); 322